Variable stiffness midsole for article of footwear

ABSTRACT

A sole structure for an article of footwear includes a bladder having a first barrier element attached to a second barrier element to define a chamber including an interior void containing a compressible fluid, a pressure of the compressible fluid being adjustable to selectively adjust a position of the first barrier element relative to the second barrier element. In addition, the sole structure includes a first plate attached to the first barrier element and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63/131,499, filed on Dec. 29, 2020. The disclosure of this prior application is considered part of the disclosure of this application and is hereby incorporated by reference in its entirety.

FIELD

The present disclosure relates generally to an article of footwear and more particularly to a sole structure for an article of footwear.

BACKGROUND

This section provides background information related to the present disclosure and is not necessarily prior art.

Articles of footwear conventionally include an upper and a sole structure. The upper may be formed from any suitable material(s) to receive, secure, and support a foot on the sole structure. The upper may cooperate with laces, straps, or other fasteners to adjust the fit of the upper around the foot. A bottom portion of the upper, proximate to a bottom surface of the foot, attaches to the sole structure.

Sole structures generally include a layered arrangement extending between a ground surface and the upper. For example, a sole structure may include a midsole and an outsole. The midsole is generally disposed between the outsole and the upper and provides cushioning for the foot. The outsole provides abrasion-resistance and traction with the ground surface and may be formed from rubber or other materials that impart durability and wear-resistance, as well as enhance traction with the ground surface.

While conventional sole structures adequately provide a wearer with cushioning and traction, such sole structures include fixed properties. For example, an overall stiffness of a conventional sole structure is not adjustable but, rather, is fixed based on the materials used in constructing the sole structure. As such, conventional sole structures may be designed and function well for a particular activity but may be lacking when the same sole structure is used for a different activity requiring different responsiveness and/or cushioning.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected configurations and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a lateral side perspective view of an article of footwear including an example sole structure according to the present disclosure;

FIG. 2 is a top-front exploded perspective view of the sole structure of FIG. 1;

FIG. 3 is a bottom-rear exploded perspective view of the sole structure of FIG. 1;

FIG. 4 is a cross-sectional view of the sole structure of FIG. 1, taken along Line 4-4 in FIG. 1;

FIG. 5 is an exploded cross-sectional view of the sole structure of FIG. 4;

FIG. 6 is a cross-sectional view of the sole structure of FIG. 4, taken along Line 6-6 in FIG. 4;

FIG. 7 is an exploded view of a stack of fiber sheets used to form a plate in accordance with the principles of the present disclosure; and

FIG. 8 is an exploded view of a stack of fiber sheets used to form a plate in accordance with the principles of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

Example configurations will now be described more fully with reference to the accompanying drawings. Example configurations are provided so that this disclosure will be thorough, and will fully convey the scope of the disclosure to those of ordinary skill in the art. Specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of configurations of the present disclosure. It will be apparent to those of ordinary skill in the art that specific details need not be employed, that example configurations may be embodied in many different forms, and that the specific details and the example configurations should not be construed to limit the scope of the disclosure.

The terminology used herein is for the purpose of describing particular exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. Additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” “attached to,” or “coupled to” another element or layer, it may be directly on, engaged, connected, attached, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” “directly attached to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

The terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections. These elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example configurations.

In one configuration, a sole structure for an article of footwear includes a bladder having a first barrier element attached to a second barrier element to define a chamber including an interior void containing a compressible fluid, a pressure of the compressible fluid being adjustable to selectively adjust a position of the first barrier element relative to the second barrier element. In addition, the sole structure includes a first plate attached to the first barrier element and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate.

The sole structure may include one or more of the following optional features. For example, the chamber may include a valve in fluid communication with the interior void. Additionally or alternatively, each of the bladder, the first plate, and the second plate may extend from a forefoot region of the sole structure to a heel region of the sole structure. Further, a stiffness of the first plate may be different than a stiffness of the second plate.

In one configuration, the bladder may include a tensile element disposed within the interior void. The tensile element may include a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.

Each of the first plate and the second plate may include a laminate fiber structure having a plurality of fiber layers consolidated by a resin. At least one of the first plate and the second plate may include at least four of the fiber layers.

A pump may be in fluid communication with the interior void. Additionally or alternatively, the bladder, the first plate, and the second plate may include the same size and shape.

In another configuration, a sole structure for an article of footwear includes a first barrier element attached to a second barrier element to define a chamber having an interior void, a first plate attached to the first barrier element, and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate. A distance between the first plate and the second plate is selectively adjustable by varying a volume of fluid contained within the interior void.

The sole structure may include one or more of the following optional features. For example, the chamber may include a valve in fluid communication with the interior void. Additionally or alternatively, each of the bladder, the first plate, and the second plate may extend from a forefoot region of the sole structure to a heel region of the sole structure. Further, a stiffness of the first plate may be different than a stiffness of the second plate.

In one configuration, a tensile element may be disposed within the interior void. The tensile element may include a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.

Each of the first plate and the second plate may include a laminate fiber structure including a plurality of fiber layers consolidated by a resin. At least one of the first plate and the second plate may include at least four of the fiber layers.

A pump may be in fluid communication with the interior void. Further, an article of footwear may incorporate the sole structure.

In another configuration, a composite structure for an article of footwear includes a bladder having a first barrier element attached to a second barrier element to define a chamber including an interior void, a first plate attached to the first barrier element, and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate. A stiffness of the composite structure is adjustable.

The sole structure may include one or more of the following optional features. For example, a distance between the first plate and the second plate may be selectively adjustable to adjust the stiffness of the composite structure. The distance between the first plate and the second plate may adjustable by varying a volume of a fluid contained within the interior void, by varying a pressure of a fluid contained within the interior void, and/or by varying a thickness of the bladder.

A pump may be in fluid communication with the interior void and may be operable to selectively supply the interior void with a fluid.

In one configuration, a tensile element may be disposed within the interior void. The tensile element may include a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.

A sole structure may incorporate the composite structure. Further, an article of footwear may incorporate the sole structure and/or the composite structure.

The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description, the drawings, and the claims.

Referring to FIG. 1, an article of footwear 10 includes a sole structure 100 and an upper 200 attached to the sole structure 100. The footwear 10 may further include an anterior end 12 associated with a forward-most point of the footwear, and a posterior end 14 corresponding to a rearward-most point of the footwear 10. A longitudinal axis A₁₀ of the footwear 10 extends along a length of the footwear 10 from the anterior end 12 to the posterior end 14 parallel to a ground surface, and generally divides the footwear 10 into a medial side 16 and a lateral side 18. Accordingly, the medial side 16 and the lateral side 18 respectively correspond with opposite sides of the footwear 10 and extend from the anterior end 12 to the posterior end 14. As used herein, a longitudinal direction refers to the direction extending from the anterior end 12 to the posterior end 14, while a lateral direction refers to the direction transverse to the longitudinal direction and extending from the medial side 16 to the lateral side 18.

The article of footwear 10 may be divided into one or more regions. The regions may include a forefoot region 20, a mid-foot region 22, and a heel region 24. The forefoot region 20 may correspond with the phalanges and the metatarsal bones of a foot. The mid-foot region 22 may correspond with an arch area of the foot, and the heel region 24 may correspond with rear portions of the foot, including a calcaneus bone.

The article of footwear 10, and more particularly, the sole structure 100, may be further described as including a peripheral region 26 and an interior region 28, as indicated in FIG. 1. The peripheral region 26 is generally described as being a region between the interior region 28 and an outer perimeter of the sole structure 100. Particularly, the peripheral region 26 extends from the forefoot region 20 to the heel region 24 along each of the medial side 16 and the lateral side 18, and wraps around each of the forefoot region 20 and the heel region 24. The interior region 28 is circumscribed by the peripheral region 26, and extends from the forefoot region 20 to the heel region 24 along a central portion of the sole structure 100. Accordingly, each of the forefoot region 20, the mid-foot region 22, and the heel region 24 may be described as including the peripheral region 26 and the interior region 28.

The sole structure 100 includes a midsole 102 configured to provide cushioning and support and an outsole 104 defining a ground-engaging surface of the sole structure 100. Unlike conventional sole structures, which include monolithic midsoles and an outsole, the sole structure 100 of the present disclosure is configured as a composite structure including a plurality of components joined together. For example, the midsole 102 includes an upper cushion element 106, a lower cushion element 108, and an inner cushion element 110 arranged in a layered configuration. The midsole 102 is further defined by a top surface 122 facing the upper 200, a bottom surface 124 formed on an opposite side of the midsole 102 than the top surface 122 and facing away from the upper 200, and a peripheral side surface 126 extending between the top surface 122 and the bottom surface 124 and defining an outer periphery of the midsole 102. The top surface 122 of the midsole 102 includes a foot cavity that defines a footbed 132 of the sole structure 100 extending continuously from the anterior end 12 to the posterior end 14 of the footwear 10. The bottom surface 124 of the midsole 102 defines a profile of a ground-engaging surface of the sole structure 100 and may be at least partially covered by the outsole 104 when the sole structure 100 is assembled.

FIGS. 2 and 3 provide an exploded view of the sole structure 100 showing the outsole 104, the lower cushion element 108, the upper cushion element 106, and the inner cushion element 110 disposed between the lower cushion element 108 and the upper cushion element 106. The inner cushion element 110 further includes a first plate 112 a, a bladder 114, and a second plate 112 b formed on an opposite side of the bladder 114 than the first plate 112 a. The first plate 112 a and the second plate 112 b may be formed from a material having a significantly higher Young's modulus than the bladder 114. For example, the plates 112 a, 112 b may have a Young's modulus of at least 120 GPa, while the bladder 114 may have a Young's modulus of 4 GPa or lower.

As discussed below with reference to FIGS. 6-8, the stiffness of the inner cushion element 110 is adjustable to allow the user to adjust the fit and stiffness of the sole structure 100. Specifically, when the inner cushion element 110 is assembled, the stiffness of the inner cushion element 110 may be adjusted by inflating or deflating the bladder 114 disposed between the first plate 112 a and the second plate 112 b. By inflating the bladder 114, a thickness T₁₁₄ of the bladder 114 increases and causes a distance between the first plate 112 a and the second plate 112 b to increase. The increased distance from the first plate 112 a to the second plate 112 b increases the stiffness of the inner cushion element 110. Conversely, deflating the bladder 114 causes a thickness T₁₁₄ of the bladder 114 to decrease. This decrease in thickness causes the distance between the first plate 112 a and the second plate 112 b to likewise decrease, which results in the stiffness of the inner cushion element 110 decreasing. In sum, decreasing the thickness T₁₁₄ of the bladder 114 provides a more flexible sole structure 100 and increasing the thickness T₁₁₄ of the bladder 114 provides a more rigid sole structure 100.

Because the stiffness of the inner cushion element 110 is dependent on the distance between the first plate 112 a and the second plate 112 b, the range of stiffness available when adjusting the inner cushion element 110 may be tuned by the selection of the thicknesses T_(112a), T_(112b) of the plates 112 a, 112 b used (e.g., by including more or less fiber layers 168 in the laminate fiber structure 166 of the plate 112). For example, when the first plate 112 a and the second plate 112 b are thinner, the bladder 114 will have a greater range of inflation without exceeding a maximum thickness of the inner cushion element 110. Conversely, when the first plate 112 a and the second plate 112 b are thicker, the bladder 114 will have a smaller range of inflation without exceeding the maximum thickness of the inner cushion element 110.

The upper cushion element 106 may include an upper surface 134 corresponding to the footbed 132 of the sole structure 100, a lower surface 136 formed on an opposite side up the upper cushion element 106 than the upper surface 134, a peripheral region 138 defining an outer periphery of the upper cushion element 106, and an interior region 140 bounded by the peripheral region 138 of the upper cushion element 106. The lower cushion element 108 may include an upper surface 142, a lower surface 144 corresponding to the bottom surface 124 of the midsole 102 and formed on an opposite side of the lower cushion element 108 than the upper surface 142, a peripheral region 146 defining an outer periphery of the lower cushion element 108, and an interior region 148 bounded by the peripheral region 146 of the lower cushion element 108. As shown in FIG. 3, a portion of the lower surface 144 of the lower cushion element 108 may include a plurality of first traction elements 186. The lower surface 136 of the upper cushion element 106 may oppose the upper surface 142 of the lower cushion element 108 and define a space or gap 150 therebetween for receiving the inner cushion element 110.

The upper cushion element 106 and the lower cushion element 108 include a resilient polymeric material, such as foam or rubber, to impart properties of cushioning, responsiveness, and energy distribution to the foot of the wearer. In the illustrated example, the upper cushion element 106 is formed of a first foam material, and the lower cushion element 108 is formed of a second foam material. For example, the upper cushion element 106 may include foam materials providing greater cushioning and impact distribution, while the lower cushion element 108 includes a foam material having a greater stiffness in order to provide increased lateral stiffness to the peripheral region 26 of the sole structure 100.

Example resilient polymeric materials for upper cushion element 106 and lower cushion element 108 may include those based on foaming or molding one or more polymers, such as one or more elastomers (e.g., thermoplastic elastomers (TPE)). The one or more polymers may include aliphatic polymers, aromatic polymers, or mixtures of both; and may include homopolymers, copolymers (including terpolymers), or mixtures of both.

In some aspects, the one or more polymers may include olefinic homopolymers, olefinic copolymers, or blends thereof. Examples of olefinic polymers include polyethylene, polypropylene, and combinations thereof. In other aspects, the one or more polymers may include one or more ethylene copolymers, such as, ethylene-vinyl acetate (EVA) copolymers, EVOH copolymers, ethylene-ethyl acrylate copolymers, ethylene-unsaturated mono-fatty acid copolymers, and combinations thereof.

In further aspects, the one or more polymers may include one or more polyacrylates, such as polyacrylic acid, esters of polyacrylic acid, polyacrylonitrile, polyacrylic acetate, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate, and polyvinyl acetate; including derivatives thereof, copolymers thereof, and any combinations thereof.

In yet further aspects, the one or more polymers may include one or more ionomeric polymers. In these aspects, the ionomeric polymers may include polymers with carboxylic acid functional groups, sulfonic acid functional groups, salts thereof (e.g., sodium, magnesium, potassium, etc.), and/or anhydrides thereof. For instance, the ionomeric polymer(s) may include one or more fatty acid-modified ionomeric polymers, polystyrene sulfonate, ethylene-methacrylic acid copolymers, and combinations thereof.

In further aspects, the one or more polymers may include one or more styrenic block copolymers, such as acrylonitrile butadiene styrene block copolymers, styrene acrylonitrile block copolymers, styrene ethylene butylene styrene block copolymers, styrene ethylene butadiene styrene block copolymers, styrene ethylene propylene styrene block copolymers, styrene butadiene styrene block copolymers, and combinations thereof.

In further aspects, the one or more polymers may include one or more polyamide copolymers (e.g., polyamide-polyether copolymers) and/or one or more polyurethanes (e.g., cross-linked polyurethanes and/or thermoplastic polyurethanes). Examples of suitable polyurethanes include those discussed below for the barrier elements 158 a, 158 b of the bladder 114. Alternatively, the one or more polymers may include one or more natural and/or synthetic rubbers, such as butadiene and isoprene.

When the resilient polymeric material is a foamed polymeric material, the foamed material may be foamed using a physical blowing agent which phase transitions to a gas based on a change in temperature and/or pressure, or a chemical blowing agent which forms a gas when heated above its activation temperature. For example, the chemical blowing agent may be an azo compound such as azodicarbonamide, sodium bicarbonate, and/or an isocyanate.

In some embodiments, the foamed polymeric material may be a crosslinked foamed material. In these embodiments, a peroxide-based crosslinking agent such as dicumyl peroxide may be used. Furthermore, the foamed polymeric material may include one or more fillers such as pigments, modified or natural clays, modified or unmodified synthetic clays, talc glass fiber, powdered glass, modified or natural silica, calcium carbonate, mica, paper, wood chips, and the like.

The resilient polymeric material may be formed using a molding process. In one example, when the resilient polymeric material is a molded elastomer, the uncured elastomer (e.g., rubber) may be mixed in a Banbury mixer with an optional filler and a curing package such as a sulfur-based or peroxide-based curing package, calendared, formed into shape, placed in a mold, and vulcanized.

In another example, when the resilient polymeric material is a foamed material, the material may be foamed during a molding process, such as an injection molding process. A thermoplastic polymeric material may be melted in the barrel of an injection molding system and combined with a physical or chemical blowing agent and optionally a crosslinking agent, and then injected into a mold under conditions which activate the blowing agent, forming a molded foam.

Optionally, when the resilient polymeric material is a foamed material, the foamed material may be a compression molded foam. Compression molding may be used to alter the physical properties (e.g., density, stiffness and/or durometer) of a foam, or to alter the physical appearance of the foam (e.g., to fuse two or more pieces of foam, to shape the foam, etc.), or both.

The compression molding process desirably starts by forming one or more foam preforms, such as by injection molding and foaming a polymeric material, by forming foamed particles or beads, by cutting foamed sheet stock, and the like. The compression molded foam may then be made by placing the one or more preforms formed of foamed polymeric material(s) in a compression mold, and applying sufficient pressure to the one or more preforms to compress the one or more preforms in a closed mold. Once the mold is closed, sufficient heat and/or pressure is applied to the one or more preforms in the closed mold for a sufficient duration of time to alter the preform(s) by forming a skin on the outer surface of the compression molded foam, fuse individual foam particles to each other, permanently increase the density of the foam(s), or any combination thereof. Following the heating and/or application of pressure, the mold is opened and the molded foam article is removed from the mold.

As shown in FIG. 6, the bladder 114 of the inner cushion element 110 includes a first barrier element 158 a attached to a second barrier element 158 b joined together at a peripheral seam 156 to define a chamber 162 having an interior void 164.

As used herein, the term “barrier element” (e.g., barrier element 158 a, 158 b) encompasses both monolayer and multilayer films. In some embodiments, one or both of barrier elements the 158 a, 158 b are each produced (e.g., thermoformed or blow molded) from a monolayer film (a single layer). In other embodiments, one or both of the barrier elements 158 a, 158 b are each produced (e.g., thermoformed or blow molded) from a multilayer film (multiple sublayers). In either aspect, each layer or sublayer can have a film thickness ranging from about 0.2 micrometers to about 1 millimeter. In further embodiments, the film thickness for each layer or sublayer can range from about 0.5 micrometers to about 500 micrometers. In yet further embodiments, the film thickness for each layer or sublayer can range from about 1 micrometer to about 100 micrometers.

One or both of the barrier elements 158 a, 158 b can independently be transparent, translucent, and/or opaque. As used herein, the term “transparent” for a barrier element and/or a fluid-filled chamber means that light passes through the barrier element in substantially straight lines and a viewer can see through the barrier element. In comparison, for an opaque barrier element, light does not pass through the barrier element and one cannot see clearly through the barrier element at all. A translucent barrier element falls between a transparent barrier element and an opaque barrier element, in that light passes through a translucent layer but some of the light is scattered so that a viewer cannot see clearly through the layer.

The barrier elements 158 a, 158 b can each be produced from an elastomeric material that includes one or more thermoplastic polymers and/or one or more cross-linkable polymers. In an aspect, the elastomeric material can include one or more thermoplastic elastomeric materials, such as one or more thermoplastic polyurethane (TPU) copolymers, one or more ethylene-vinyl alcohol (EVOH) copolymers, and the like.

As used herein, “polyurethane” refers to a copolymer (including oligomers) that contains a urethane group (—N(C═O)O—). These polyurethanes can contain additional groups such as ester, ether, urea, allophanate, biuret, carbodiimide, oxazolidinyl, isocynaurate, uretdione, carbonate, and the like, in addition to urethane groups. In an aspect, one or more of the polyurethanes can be produced by polymerizing one or more isocyanates with one or more polyols to produce copolymer chains having (—N(C═O)O—) linkages.

Examples of suitable isocyanates for producing the polyurethane copolymer chains include diisocyanates, such as aromatic diisocyanates, aliphatic diisocyanates, and combinations thereof. Examples of suitable aromatic diisocyanates include toluene diisocyanate (TDI), TDI adducts with trimethyloylpropane (TMP), methylene diphenyl diisocyanate (MDI), xylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), hydrogenated xylene diisocyanate (HXDI), naphthalene 1,5-diisocyanate (NDI), 1,5-tetrahydronaphthalene diisocyanate, para-phenylene diisocyanate (PPDI), 3,3′-dimethyldiphenyl-4, 4′-diisocyanate (DDDI), 4,4′-dibenzyl diisocyanate (DBDI), 4-chloro-1,3-phenylene diisocyanate, and combinations thereof. In some embodiments, the copolymer chains are substantially free of aromatic groups.

In particular aspects, the polyurethane polymer chains are produced from diisocynates including HMDI, TDI, MDI, H12 aliphatics, and combinations thereof. In an aspect, the thermoplastic TPU can include polyester-based TPU, polyether-based TPU, polycaprolactone-based TPU, polycarbonate-based TPU, polysiloxane-based TPU, or combinations thereof.

In another aspect, the polymeric layer can be formed of one or more of the following: EVOH copolymers, poly(vinyl chloride), polyvinylidene polymers and copolymers (e.g., polyvinylidene chloride), polyamides (e.g., amorphous polyamides), amide-based copolymers, acrylonitrile polymers (e.g., acrylonitrile-methyl acrylate copolymers), polyethylene terephthalate, polyether imides, polyacrylic imides, and other polymeric materials known to have relatively low gas transmission rates. Blends of these materials as well as with the TPU copolymers described herein and optionally including combinations of polyimides and crystalline polymers, are also suitable.

The barrier elements 158 a, 158 b may include two or more sublayers (multilayer film) such as shown in Mitchell et al., U.S. Pat. No. 5,713,141 and Mitchell et al., U.S. Pat. No. 5,952,065, the disclosures of which are incorporated by reference in their entirety. In embodiments where the barrier elements 158 a, 158 b include two or more sublayers, examples of suitable multilayer films include microlayer films, such as those disclosed in Bonk et al., U.S. Pat. No. 6,582,786, which is incorporated by reference in its entirety. In further embodiments, barrier elements 158 a, 158 b may each independently include alternating sublayers of one or more TPU copolymer materials and one or more EVOH copolymer materials, where the total number of sublayers in each of the barrier elements 158 a, 158 b includes at least four (4) sublayers, at least ten (10) sublayers, at least twenty (20) sublayers, at least forty (40) sublayers, and/or at least sixty (60) sublayers.

The chamber 162 can be produced from the barrier elements 158 a, 158 b using any suitable technique, such as thermoforming (e.g. vacuum thermoforming), blow molding, extrusion, injection molding, vacuum molding, rotary molding, transfer molding, pressure forming, heat sealing, casting, low-pressure casting, spin casting, reaction injection molding, radio frequency (RF) welding, and the like. In an aspect, the barrier elements 158 a, 158 b can be produced by co-extrusion followed by vacuum thermoforming to produce an inflatable chamber 162, which can optionally include one or more valves 120 (e.g., one way valves) that allows the chamber 162 to be filled with the fluid (e.g., gas).

The chamber 162 can be provided in a fluid-filled (e.g., as provided in footwear 10) or in an unfilled state. The chamber 162 can be filled to include any suitable fluid, such as a gas or liquid. In an aspect, the gas can include air, nitrogen (N₂), or any other suitable gas. In another aspect, the liquid can include Non-Newtonian fluid that applies more resistance when subjected to a quickly applied load. In other aspects, the chamber 162 can alternatively include other media, such as pellets, beads, ground recycled material, and the like (e.g., foamed beads and/or rubber beads). The fluid provided to the chamber 162 can result in the chamber 162 being pressurized. Alternatively, the fluid provided to the chamber 162 can be at atmospheric pressure such that the chamber 162 is not pressurized but, rather, simply contains a volume of fluid at atmospheric pressure.

The chamber 162 desirably has a low gas transmission rate to preserve its retained gas pressure. In some embodiments, the chamber 162 has a gas transmission rate for nitrogen gas that is at least about ten (10) times lower than a nitrogen gas transmission rate for a butyl rubber layer of substantially the same dimensions. In an aspect, chamber 162 has a nitrogen gas transmission rate of 15 cubic-centimeter/square-meter·atmosphere·day (cm³/m²·atm·day) or less for an average film thickness of 500 micrometers (based on thicknesses of the barrier elements 158 a, 158 b). In further aspects, the transmission rate is 10 cm³/m²·atm·day or less, 5 cm³/m²·atm·day or less, or 1 cm³/m²·atm·day or less.

The interior void 164 of the chamber 162 of the bladder 114 may receive a tensile element 176 (FIG. 6) therein. Each tensile element 176 may include a series of connecting members 178 extending between an upper tensile sheet 180 and a lower tensile sheet 182. A first outer surface 192 of the upper tensile sheet 180 may oppose and be attached to a first inner surface 172 of the first barrier element 158 a while a second outer surface 194 of the lower tensile sheet 182 may oppose and be attached to a second inner surface 174 of the second barrier element 158 b. In this manner, when the interior void 164 of the chamber 162 receives the pressurized fluid, the connecting members 178 of the tensile element 176 are placed in tension. In some implementations, the first outer surface 192 of the upper tensile sheet 180 directly opposes and is directly attached to the first inner surface 172 of the first barrier element 158 a, and the second outer surface 194 of the lower tensile sheet 182 directly opposes and is directly attached to the second inner surface 174 of the second barrier element 158 b. Because the upper tensile sheet 180 is attached to the first barrier element 158 a and the lower tensile sheet 182 is attached to the lower barrier element 158 b, the connecting members 178 retain a desired shape of the bladder 114 when the pressurized fluid is injected into interior void 164 of the chamber 162. In other implementations, the series of connecting members 178 extend between and directly attach to the first barrier element 158 a and the second barrier element 158 b.

As shown in FIG. 1, in some examples, the chamber 162 includes a valve 120 in communication with the interior void 164. In these examples, when the interior void 164 of the chamber 162 includes a compressible fluid, the pressure of the compressible fluid can be selectively adjusted. The valve 120 of the bladder 114 may operate to vary the stiffness of the sole structure 100 by varying the volume of compressible fluid in the interior void 164 of the chamber 162 of the bladder 114. Increasing the volume of the compressible fluid further inflates the bladder 114 and increases the pressure within the bladder 114. By inflating the bladder 114, the distance between the first plate 112 a and the second plate 112 b increases, thereby increasing the stiffness of the inner cushion element 110. Conversely, the valve 120 of the bladder 114 may operate to release the compressible fluid, thereby deflating the bladder 114 as pressurized fluid exits the bladder 114. By deflating the bladder 114, the distance between the first plate 112 a and the second plate 112 b decreases, which, in turn, decreases the stiffness of the inner cushion element 110. The valve 120 may allow the user to selectively increase or decrease the pressure of the compressible fluid in the interior void 164. The selective adjustment of the compressible fluid in the interior void 164 is performed while the article of footwear 10 is in a resting or uncompressed state.

Additionally or alternatively, the sole structure 100 may include a pump 116 in fluid communication with the interior void 164 of the chamber 162 through the valve 120. In these implementations, a conduit 118 connects the valve 120 of the chamber 162 to the pump 116. The pump 116 may adjust the pressure of the compressible fluid in the interior void 164 by adding or removing the compressible fluid via the conduit 118. For example, to lower the pressure, the pump 116 may remove the compressible fluid from the interior void 164 via the valve 120. Conversely, to increase the pressure, the pump 116 may add compressible fluid to the interior void 164 via the valve 120.

The pump 116 may be mechanically operated, and increase the pressure of the compressible fluid in the interior void 164 based upon a running motion of an athlete. For example, the pump 116 may be actuated by a force associated with the foot strike of the gait cycle such that the pump 116 incrementally increases the pressure within the chamber 162 at each step. Here, the pump 116 may include a resilient diaphragm or piston (neither shown) that is compressed during a stance phase (e.g., by a heel strike) of the gait cycle and then returns to the initial uncompressed state during the swing phase (e.g., when the foot is lifted) Thus, the pressure within the chamber 162 may incrementally increase with each step from a first pressure to a higher second pressure over the course of a walk or run.

FIG. 2 provides an exploded view of the sole structure 100 showing the outsole 104, the lower cushion element 108 disposed adjacent to the inner surface 130 of the outsole 104, the second plate 112 b disposed adjacent to the upper surface 142 of the lower cushion element 108, the bladder 114 disposed adjacent to the second plate 112 b, the first plate 112 a disposed adjacent to the first barrier element 158 a of the bladder 114, and the upper cushion element 106 disposed adjacent to the first plate 112 a. As shown, the interior region 148 of the lower cushion element 108 is recessed from the peripheral region 146 to form a cavity 154 in the upper surface 142 of the lower cushion element 108. The cavity 154 may be sized to receive the upper cushion element 106.

As discussed above, the upper surface 142 of the lower cushion element 108 and the lower surface 136 of the upper cushion element 106 may cooperate to define a gap 150 therebetween for receiving the inner cushion element 110 including the first plate 112 a, the bladder 114, and the second plate 112 b. Accordingly, the inner cushion element 110 may partially occupy the gap 150 between the recessed upper surface 142 of the lower cushion element 108 and the lower surface 136 of the upper cushion element 106. Alternatively, the inner cushion element 110 may occupy the entire gap 150 between the recessed upper surface 142 of the lower cushion element 108 and the upper cushion element 106. The inner cushion element 110 may compress resiliently between the upper cushion element 106 and the lower cushion element 108.

FIG. 3 provides an exploded view of the sole structure 100 showing the lower surface 136 of the upper cushion element 106 disposed adjacent to the first plate 112 a, the first plate 112 a disposed adjacent to the first barrier element 158 a of the bladder 114, the second barrier element 158 b of the bladder 114 disposed adjacent to the second plate 112 b, the second plate 112 b disposed adjacent to the lower cushion element 108, and the lower surface 144 of the lower cushion element 108 disposed adjacent to an inner surface 130 of the outsole 104.

The first plate 112 a of the inner cushion element 110 is attached to the first barrier element 158 a and the second plate 112 b of the inner cushion element 110 is attached to the second barrier element 158 b on an opposite side of the bladder 114 than the first plate 112 a. With reference to FIGS. 7 and 8, examples of the plate 112 are shown as including laminate fiber structures 166 a, 166 b having a series of stacked fiber layers 168 a-168 d, 168 e-168 j, respectively. Each of the stacked fiber layers 168 a-168 d, 168 e-168 j may be a unidirectional tape or a multi-axial fabric having a series of fibers 160 that are impregnated and consolidated with resin 170. The resin 170 may include a two part epoxy-amine resin manufactured by Applied Poleramics, Inc. under the tradename CR-157A/DD3-76-6B. The concentration of resin 170 may range from about 25% to about 45%, and more preferably from about 30% to about 35%. The fibers 160 may include at least one of carbon fibers, aramid fibers, boron fibers, glass fibers, and other polymer fibers that form the unidirectional sheet or multi-axial fabric. Fibers such as carbon fibers, aramid fibers, and boron fibers may provide a high Young's modulus while glass fibers (e.g., fiberglass) and other polymer fibers (e.g., synthetic fibers such as polyamides other than aramid, polyesters, and polyolefins) provide a medium modulus. Alternatively, some of the fiber layers 168 a-168 d, 168 e-168 j may be a unidirectional tape while others of the fiber layers 168 a-168 d, 168 e-168 j are a multi-axial fabric. Further, each of the fiber layers 168 a-168 d, 168 e-168 j may include fibers 160 formed from the same material or, alternatively, one or more of the fiber layers 168 a-168 d, 168 e-168 j includes fibers 160 formed from a different material than the fibers 160 of the other fiber layers 168 a-168 d, 168 e-168 j.

During manufacturing of the laminate fiber structure 166, unidirectional tape or multi-axial fabric is provided and is cut into fiber plies. The plies are cut out and angled with respect to one another and the shapes of the various fiber layers 168 a-168 d, 168 e-168 j are cut from the stacked plies into the shapes shown in FIGS. 7 and 8. In so doing, the fiber layers 168 a-168 d, 168 e-168 j include fibers 160 formed at different angles relative to one another such that a longitudinal axis of the fibers 160 of the unidirectional tape or multi-axial fabric is positioned at an angle Φ relative to a longitudinal axis A₁₆₈ of each fiber layers 168 a-168 d, 168 e-168 j. Accordingly, when the fiber layers 168 a-168 d, 168 e-168 j are stacked on one another, the longitudinal axes of the fibers 160 are positioned at different angles relative to the longitudinal axis A₁₆₈ of the laminate fiber structures 166 a, 166 b.

Referring to FIG. 7, the angle Φ of fiber layers 168 a and 168 d is 15 degrees (15°), and the angle Φ of fiber layers 168 b and 168 c is −15 degrees (−15°). When manufacturing the laminate fiber structure 166 a, the plies are stacked such that when the fiber layers 168 a-168 d are cut from the stacked plies, the fiber layers 168 a-168 d have the shapes shown in FIG. 7. Namely, the bottom fiber layer 168 d includes fibers 160 positioned at 15° relative to the longitudinal axis A₁₆₈, the next fiber layer 168 c includes fibers 160 positioned at −15° relative to the longitudinal axis A₁₆₈, the next fiber layer 168 b includes fibers 160 positioned at −15° relative to the longitudinal axis A₁₆₈, and top and final fiber layer 168 a includes fibers 160 positioned at 15° relative to the longitudinal axis A₁₆₈.

Referring to FIG. 8, the angle Φ of fiber layers 168 e and 168 j is zero degrees (0°), the angle Φ of fiber layers 168 f and 168 i is 15 degrees (15°), and the angle Φ of fiber layers 16 g and 168 h is −15 degrees)(−15°. When manufacturing the laminate fiber structure 168 b, the plies are stacked such that when the fiber layers 168 e-168 j are cut from the stacked plies, the fiber layers 168 e-168 j have the shapes shown in FIG. 8. Namely, the bottom fiber layer 168 j includes fibers 160 positioned at 0° relative to the longitudinal axis A₁₆₈, the next fiber layer 168 i includes fibers 160 positioned at 15° relative to the longitudinal axis A₁₆₈, the next two fiber layers 168 g and 168 h includes fibers 160 positioned at −15° relative to the longitudinal axis A₁₆₈, the next fiber layer 168 f includes fibers 160 positioned at 15° relative to the longitudinal axis A₁₆₈, and the top and final fiber layer 168 e includes fibers 160 positioned at 0° relative to the longitudinal axis A₁₆₈.

Once the plies are stacked and cut into the fiber layers 158 a-158 d, 158 e-158 j, the stack is subjected to heat and pressure to impart the specific shape of the laminate fiber structures 166 a, 166 b to the staked layers 158 a-158 d, 158 e-158 j, respectively. Additionally, when fibers that are pre-impregnated with resin 170 are used, subjecting the stack to heat and pressure can melt or soften the pre-impregnated resin 170 and affix the plies together and hold them in the specific shape. Alternatively or additionally, a liquid resin 170 can be applied to the plies to affix the plies together and in some cases to consolidate the fibers, thereby increasing the tensile strength of the plate 112 once the resin 170 has solidified.

The plates 112 include a material providing relatively high strength and stiffness, such as polymeric material and/or composite materials. In some examples, the plate is a unidirectional carbon fiber composite. In other examples, the plate is a composite material manufactured using fiber sheets or textiles, including pre-impregnated (i.e., “prepreg”) fiber sheets or textiles. Alternatively or additionally, the plate may be manufactured by strands formed from multiple filaments of one or more types of fiber (e.g., fiber tows) by affixing the fiber tows to a substrate or to each other to produce a plate having the strands of fibers arranged predominately at predetermined angles or in predetermined positions. When using strands of fibers, the types of fibers included in the strand can include synthetic polymer fibers which can be melted and re-solidified to consolidate the other fibers present in the strand and, optionally, other components such as stitching thread or a substrate or both. Alternatively or additionally, the fibers of the strand and, optionally the other components such as stitching thread or a substrate or both, can be consolidated by applying a resin after affixing the strands of fibers to the substrate and/or to each other.

In some implementations, the plate includes a substantially uniform thickness. In some examples, the thickness of the plate ranges from about 0.6 millimeters (mm) to about 3.0 mm. In one example, the thickness of the plate is substantially equal to one 1.0 mm. In other implementations, the thickness of the plate is non-uniform such that the plate may have a greater thickness in one region 20, 22, 24 of the sole structure 100 than the thicknesses in the other regions 20, 22, 24.

As discussed above, the stiffness of the sole structure 100 may be adjusted by modifying the parameters of one or more of the components 112, 114 in the layered configuration of the inner cushion element 110. For example, the stiffness (Young's modulus) and/or thicknesses T₁₁₂ of the plates 112 a, 112 b may be selected depending on a desired range of adjustment for the stiffness of the sole structure 100. In some implementations, the inner cushion element 110 may include the first plate 112 a and the second plate 112 b each having the same number of fiber layers 168 (e.g., four layers or six layers). Alternatively, the inner cushion element 110 may include a first plate 112 a and a second plate 112 b having different numbers of the fiber layers 168. For example, one of the plates 112 a may include four fiber layers 168 a-168 d and the other one of the plates may include six of the fiber layers 168 e-168 j. Providing plates 112 a, 112 b with a greater thickness T₁₁₂ provides the inner cushion element 110 with a relatively high minimum stiffness, but minimizes the range of stiffness that can be achieved by adjusting the pressure of the bladder 114. In contrast, using plates 112 a, 112 b with lower thicknesses T₁₁₂ minimizes the inherent stiffness of the inner cushion element 110, but maximizes the range of stiffness that can be achieved by adjusting the pressure and thickness T₁₁₄ of the bladder 114.

The outsole 104 is formed of a resilient polymeric material extending from a first end 196 at the anterior end 12 to a second end 198 at the posterior end 14 and includes a greater rigidity than the midsole 102. In this example, the first end 196 wraps up and around the anterior end 12 of the footwear 10. Accordingly, the outsole 104 covers the bottom surface 124 of the midsole 102 from the anterior end 12 to the posterior end 14 of the footwear 10. The outsole 104 includes a ground engaging surface 128 formed on an opposite side of the outsole 104 than the inner surface 130, apertures 184 extending through the outsole 104 from the inner surface 130 to the ground engaging surface 128, and a cutout 190 in the interior region 28 of the mid-foot region 22. The cutout 190 extends through the interior mid-foot region 22 of the outsole 104 such that the interior region 28 of the mid-foot region 22 of the midsole 102 is exposed to the ground surface through the cutout 190. The cutout 190 in the arch interior region 28 of the mid-foot region 22 provides the outsole 104 with a decreased surface area extending across a width of the outsole 104. As such, the cutout 190 locally weakens the outsole 104 to permit the outsole 104 and, thus, the sole structure 100, to bend and twist a desired amount at the mid-foot region 22.

The ground engaging surface 128 includes a plurality of second traction elements 188 arranged along a length of the outsole 104. The plurality of second traction elements 188 includes a plurality of nubs or protrusions integrally formed of the same material as the outsole 104. Traction elements of the plurality of first traction elements 186 formed on the lower surface 144 of the lower cushion element 108 are exposed to the ground through the cutout 190 of the outsole 104 when the sole structure 100 is assembled. The plurality of first traction elements 186 includes a plurality of nubs or protrusions integrally formed of the same material as the lower cushion element 108, and having a height that is greater than a height of the second traction elements 188 so that the plurality of first traction elements 186 and the plurality of second traction elements 188 extend away from the sole structure 100 and terminate on the same plane. As shown in FIG. 3, the plurality of first and second traction elements 186, 188 may be pentagonal in shape, or any other shape suitable for ground engagement.

The upper 200 forms an enclosure having plurality of components that cooperate to define an interior void 202 and an ankle opening 204 in the heel region 24, which cooperate to receive and secure a foot for support on the sole structure 100. In some examples, one or more fasteners 206 extend along the upper 200 to adjust a fit of the interior void 202 around the foot while concurrently accommodating entry and removal of the foot therefrom. The upper 200 may include apertures such as eyelets and/or other engagement features such as fabric or mesh loops that receive the fasteners 206. The fasteners 206 may include laces, straps, cords, hook-and-loop, or any other suitable type of fastener. The upper 200 may include a tongue portion 210 that extends between the interior void 202 and the fasteners 206.

The upper 200 may be formed from one or more materials that are stitched or adhesively bonded together to define the interior void 202. Suitable materials of the upper 200 may include, but are not limited to, textiles, foam, leather, and synthetic leather. The example upper 200 may be formed from a combination of one or more substantially inelastic or non-stretchable materials and one or more substantially elastic or stretchable materials disposed in different regions of the upper 200 to facilitate movement of the article of footwear 10 between the tightened state and the loosened state. The one or more elastic materials may include any combination of one or more elastic fabrics such as, without limitation, spandex, elastane, rubber or neoprene. The one or more inelastic materials may include any combination of one or more of thermoplastic polyurethanes, nylon, leather, vinyl, or another material/fabric that does not impart properties of elasticity.

The following Clauses provide an exemplary configuration for a sole structure for an article of footwear, an article of footwear, and a composite structure described above.

Clause 1. A sole structure for an article of footwear, the sole structure comprising a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void containing a compressible fluid, a pressure of the compressible fluid being adjustable to selectively adjust a position of the first barrier element relative to the second barrier element, a first plate attached to the first barrier element, and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate.

Clause 2. The sole structure of Clause 1, wherein the chamber includes a valve in fluid communication with the interior void.

Clause 3. The sole structure of any of the preceding Clauses, wherein each of the bladder, the first plate, and the second plate extends from a forefoot region of the sole structure to a heel region of the sole structure.

Clause 4. The sole structure of any of the preceding Clauses, wherein a stiffness of the first plate is different than a stiffness of the second plate.

Clause 5. The sole structure of any of the preceding Clauses, wherein the bladder includes a tensile element disposed within the interior void.

Clause 6. The sole structure of Clause 5, wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.

Clause 7. The sole structure of any of the preceding Clauses, wherein each of the first plate and the second plate includes a laminate fiber structure including a plurality of fiber layers consolidated by a resin.

Clause 8. The sole structure of Clause 7, wherein at least one of the first plate and the second plate includes at least four of the fiber layers.

Clause 9. The sole structure of Clause 7, further comprising a pump in fluid communication with the interior void.

Clause 10. The sole structure of any of the preceding Clauses, wherein the bladder, the first plate, and the second plate include the same size and shape.

Clause 11. A sole structure for an article of footwear, the sole structure comprising a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void, a first plate attached to the first barrier element, and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate, a distance between the first plate and the second plate being selectively adjustable by varying a volume of fluid contained within the interior void.

Clause 12. The sole structure of Clause 11, wherein the chamber includes a valve in fluid communication with the interior void.

Clause 13. The sole structure of any of the preceding Clauses, wherein each of the bladder, the first plate, and the second plate extends from a forefoot region of the sole structure to a heel region of the sole structure.

Clause 14. The sole structure of any of the preceding Clauses, wherein a stiffness of the first plate is different than a stiffness of the second plate.

Clause 15. The sole structure of any of the preceding Clauses, further comprising a tensile element disposed within the interior void.

Clause 16. The sole structure of Clause 15, wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.

Clause 17. The sole structure of any of the preceding Clauses, wherein each of the first plate and the second plate includes a laminate fiber structure including a plurality of fiber layers consolidated by a resin.

Clause 18. The sole structure of Clause 17, wherein at least one of the first plate and the second plate includes at least four of the fiber layers.

Clause 19. The sole structure of Clause 17, further comprising a pump in fluid communication with the interior void.

Clause 20. An article of footwear incorporating the sole structure of any of the preceding Clauses.

Clause 21. A composite structure for an article of footwear, the composite structure comprising a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void, a first plate attached to the first barrier element, and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate, a stiffness of the composite structure being adjustable.

Clause 22. The composite structure of Clause 21, wherein a distance between the first plate and the second plate is selectively adjustable to adjust the stiffness of the composite structure.

Clause 23. The composite structure of Clause 22, wherein the distance between the first plate and the second plate is adjustable by varying a volume of a fluid contained within the interior void.

Clause 24. The composite structure of Clause 22, wherein the distance between the first plate and the second plate is adjustable by varying a pressure of a fluid contained within the interior void.

Clause 25. The composite structure of Clause 22, wherein the distance between the first plate and the second plate is adjustable by varying a thickness of the bladder.

Clause 26. The composite structure of Clause 22, further comprising a pump in fluid communication with the interior void and operable to selectively supply the interior void with a fluid.

Clause 27. The composite structure of any of the preceding Clauses, further comprising a tensile element disposed within the interior void.

Clause 28. The composite structure of Clause 27, wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.

Clause 29. A sole structure incorporating the composite structure of any of the preceding Clauses.

Clause 30. An article of footwear incorporating the composite structure of any of the preceding Clauses.

The foregoing description has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular configuration are generally not limited to that particular configuration, but, where applicable, are interchangeable and can be used in a selected configuration, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. A sole structure for an article of footwear, the sole structure comprising: a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void containing a compressible fluid, a pressure of the compressible fluid being adjustable to selectively adjust a position of the first barrier element relative to the second barrier element; a first plate attached to the first barrier element; and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate.
 2. The sole structure of claim 1, wherein the chamber includes a valve in fluid communication with the interior void.
 3. The sole structure of claim 1, wherein each of the bladder, the first plate, and the second plate extends from a forefoot region of the sole structure to a heel region of the sole structure.
 4. The sole structure of claim 1, wherein a stiffness of the first plate is different than a stiffness of the second plate.
 5. The sole structure of claim 1, wherein the bladder includes a tensile element disposed within the interior void.
 6. The sole structure of claim 5, wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.
 7. The sole structure of claim 1, wherein each of the first plate and the second plate includes a laminate fiber structure including a plurality of fiber layers consolidated by a resin.
 8. The sole structure of claim 7, wherein at least one of the first plate and the second plate includes at least four of the fiber layers.
 9. The sole structure of claim 7, further comprising a pump in fluid communication with the interior void.
 10. The sole structure of claim 1, wherein the bladder, the first plate, and the second plate include the same size and shape.
 11. A sole structure for an article of footwear, the sole structure comprising: a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void; a first plate attached to the first barrier element; and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate, a distance between the first plate and the second plate being selectively adjustable by varying a volume of fluid contained within the interior void.
 12. The sole structure of claim 11, wherein the chamber includes a valve in fluid communication with the interior void.
 13. The sole structure of claim 11, wherein each of the bladder, the first plate, and the second plate extends from a forefoot region of the sole structure to a heel region of the sole structure.
 14. The sole structure of claim 11, wherein a stiffness of the first plate is different than a stiffness of the second plate.
 15. The sole structure of claim 11, further comprising a tensile element disposed within the interior void.
 16. The sole structure of claim 15, wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer.
 17. The sole structure of claim 11, wherein each of the first plate and the second plate includes a laminate fiber structure including a plurality of fiber layers consolidated by a resin.
 18. The sole structure of claim 17, wherein at least one of the first plate and the second plate includes at least four of the fiber layers.
 19. The sole structure of claim 17, further comprising a pump in fluid communication with the interior void.
 20. An article of footwear incorporating the sole structure of claim
 11. 